I use Ubuntu’s Uncomplicated firewall because it is available on Ubuntu and it's very simple.
if ufw is not installed by default be sure to install it first.
sf2-ddd | |
├── app | |
├── bin | |
├── build | |
├── lib | |
├── src | |
│ └── __VendorPrefix | |
│ ├── Application | |
│ │ └── __DomainNameBundle | |
│ │ ├── Command |